This invention relates to improvements in and relating to one-touch action type power windows for vehicles which have a retaining circuit for raising or lowering window glass by one-touch operation on a switch.
For the purpose of stopping a motor as soon as window glass is completely opened or closed or when a finger is caught in the window, the conventional one-touch action type power windows are usually provided with a pulse generator in the motor, to supply a signal indicative of the rotational speed of the motor to the retaining circuit thereby to control the same to stop the motor. However, the provision of the pulse generator which usually has a complicate construction requires a higher production cost and will invite various troubles during use of the power window. For these reasons, there has been a strong demand for a simple and reliable one-touch action type power window.
The present invention therefore has as its object the provision of a simple and reliable one-touch action type power window.
It is another object of the present invention to provide a one-touch action type power window which allows a greater degree of freedom in designing.
It is still another object of the invention to provide an energy-saving one-touch action type power window which can contribute to avoid unnecessary consumption of electric current.
According to the instant invention, and for the purpose of attaining the just-mentioned objects, there is provided a one-touch action type power window which comprises in combination: a change-over switch connected to a power source and having a movable contact returnable automatically to a neutral position upon removal therefrom of an operating force and UP and DOWN contacts located opposingly on opposite sides of said movable contact; a reversible motor connect to said UP and DOWN contacts to drive a window operator to raise or lower the window glass; a retaining circuit having an input terminal connected said UP and DOWN contacts and an output terminal to said motor, and adapted to hold said motor in an actuated state upon closing said change-over switch on said UP or DOWN contact and after removal of said operating force from said change-over switch; detecting means located close to a wire through which the operating current of said motor flows and adapted to generate a varying voltage in response to variations occurring in the electric field around said wire due to interruptions of said motor operating current; and a control circuit having an input terminal connected to said detecting means and an output terminal to said retaining circuit, and adapted to detect the rotational speed of said motor from said varying voltage and to actuate said retaining circuit only when said rotational speed of said motor is above a predetermined value.
In a preferred form of the invention, the detecting means is provided in the form of a pick-up coil which picks up the frequency of the interrupted current in terms of voltage variations. The pick-up coil converts the variations in the electric field surrounding the wire alternately into voltage variations according to the law of electromagnetic induction, the obtained alternative current being fed to a control circuit to produce through D-A conversion a signal voltage varying in proportion to the rotational speed of the motor. The control circuit controls the retaining circuit in response to the signal voltage to stop the motor. The pick-up coil is extremely simple in construction and involve no complicate structure as would cause troubles during use, thus permitting to fabricate a one-touch action type power window which is simple in construction and reliable in operation as compared with conventional counterparts which have a pulse generator within the motor. The pick-up coil may be located in any position as long as it is suitably associated with the operating current of the motor and thus allows a greater degree of freedom in designing. Furthermore, the pick-up coil contributes to save the battery power as it utilizes the motor operating current.
The above and other objects, features and advantages of the invention will become apparent from the following description and appended claims taken in conjunction with the accompanying drawings which show by way of example a preferred embodiment of the invention.